1. Field of the Invention
An embodiment of the present invention relates generally to semiconductor memories and, more particularly, to methods of programming semiconductor memories.
2. Description of Related Art
Charge-trapping memories, commonly referred to as flash memories, find extensive use in a wide range of electronic devices including cameras, cellular telephones and personal digital assistants as well as modems, laptop computers and the like. Charge-trapping memories are capable of storing relatively large amounts of data in relatively small spaces. Data stored in charge-trapping memories maintains its integrity even in the absence of applied power.
A cell of a charge-trapping memory can be programmed by modifying a threshold voltage associated with the cell. Reading data from the cell can be accomplished by applying a reference voltage and detecting a current level. A single-level cell (SLC) is programmable to one of two distinguishable threshold levels for storage of one bit of information. When, for example, four or eight distinguishable threshold levels can be supported by the cell, the cell can be capable of storing, respectively, two or three bits of data. A cell that can store more than one bit of data has been referred to as a multi-level cell (MLC).
The time required to program (i.e., write to) a charge-trapping memory can be relatively large compared to that required to read from the memory. In applications involving electronic devices where data is to be stored as rapidly as possible (e.g., in a digital camera), lengthy programming times can act to hamper efficiency of operation of the memory to the detriment of overall device performance.
A need thus exists in the prior art to reduce the programming time in charge-trapping memories.